Hundreds of ruins and artifacts document nearly 1,000 years of cultural development in the Southwest. The Pueblo III period, lasting from the 12th until the beginning of the 14th century, is noted for the construction of;immense cliff dwellings, communal habitations built of stone, mud mortar, and wood on the ledges of the cliffs and protected by rock overhangs.
The most impressive of the ruins is the Cliff Palace at Mesa Verde. Dating from the Pueblo III period, it contained more than 200 rooms and over 23 ceremonial chambers, called kivas. Other notable ruins are Balcony House, Long House, and Square Tower House, all built during the 12th and 13th centuries. After a.d. 1300 the inhabitants of Mesa Verde abandoned their villages and moved away, perhaps because of raids by hostile nomads, perhaps because of prolonged periods of extreme drought.
For centuries the cliff dwellings were abandoned and forgotten, but at the end of the 19th century they were rediscovered by the Wetherill Brothers of Colorado, who also discovered Kiet Siel in Arizona. Kiet Siel, which stands for "broken pottery" in Navajo, is a well preserved cliff dwelling of the ancient Anasazi people located in a branch of the Tsegi Canyon in Northeastern Arizona. The site was first occupied at around AD 1250. At its peak, its believed that up to 150 people inhabited this site at one time. Kiet Siel, along with Betatakin and Inscription House, are the three cliff dwelling sites that make up the now protected Navajo National Monument.; Due to the;dry climate and natural overhanging cliff, the conditions at Kiet Siel were quite optimal for excellent preservation of the sites dwellings and artifacts. Kiet Siel is considered by many archaeological experts to be one of the best preserved larger ruins in the Southwest.